Plant and method for producing liquefied natural gas

ABSTRACT

A plant for producing liquefied natural gas comprises a carbon dioxide recovery apparatus for natural gas absorbing and removing carbon dioxide from natural gas, a liquefying apparatus having a steam turbine, for liquefying the natural gas from which carbon dioxide has been removed by the carbon dioxide recovery apparatus, a boiler equipment for supplying steam to the steam turbine of the liquefying apparatus, and a carbon dioxide recovery apparatus for combustion exhaust gas including an absorption tower for absorbing carbon dioxide from combustion exhaust gas exhausted from the boiler equipment by absorbing liquid, and a regeneration tower for separating and recovering carbon dioxide from the absorbing liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2002-240814, filed Aug. 21, 2002;the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plant and method for producingliquefied natural gas.

2. Description of the Related Art

Recently, liquefied natural gas (LNG) has attracted attention as a cleanenergy source. LNG is produced in an LNG plant by removing carbondioxide (CO₂) and sulfur components, such as hydrogen sulfide (H₂S),from natural gas and removing the moisture content, and then liquefyingthe resultant gas in a liquefying apparatus. Specifically, CO₂ isremoved from natural gas so that 50 ppm or less of CO₂ remains toprevent generation of dry ice during the LPG production process.

In such an LNG production method, a large amount of combustion exhaustgas containing CO₂ is produced by a power source (e.g., boiler) fordriving a CO₂ recovery apparatus for removing CO₂ from natural gas, anda liquefying apparatus. Since CO₂ is released into the air as it is, itcauses environmental problems including global warming.

The present invention is directed to providing a plant and method forproducing liquefied natural gas, which comprises recovering CO₂contained in natural gas and in a combustion exhaust gas generated froma power source, compressing the recovered CO₂ by a compressor, feedingout the compressed CO₂ from the system by feeding it to a plant such asa urea plant, methanol plant, dimethyl ether plant, or lamp oil/lightoil synthesis plant (GTL plant), or the ground, thereby preventing orsuppressing emission of CO₂ to the air.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided aplant for producing liquefied natural gas comprising:

a carbon dioxide recovery apparatus for natural gas absorbing andremoving carbon dioxide from natural gas;

a liquefying apparatus having a steam turbine, for liquefying thenatural gas from which carbon dioxide has been removed by the carbondioxide recovery apparatus;

a boiler equipment for supplying steam to the steam turbine of theliquefying apparatus; and

a carbon dioxide recovery apparatus for combustion exhaust gas includingan absorption tower for absorbing carbon dioxide from combustion exhaustgas exhausted from the boiler equipment by absorbing liquid, and aregeneration tower for separating and recovering carbon dioxide from theabsorbing liquid.

In the plant for producing liquefied natural gas, it is preferable thatthe carbon dioxide recovery apparatus for natural gas has an absorptiontower for absorbing carbon dioxide from natural gas by absorbing liquid,and a regeneration tower for separating and recovering carbon dioxidefrom the absorbing liquid and that the regeneration tower also serves asthe regeneration tower of the carbon dioxide recovery apparatus forcombustion exhaust gas.

According to another aspect of the present invention, there is provideda method for producing liquefied natural gas comprising the steps of:

providing a plant for producing liquefied natural gas comprising:

(a) a carbon dioxide recovery apparatus for natural gas absorbing andremoving carbon dioxide from natural gas,

(b) a liquefying apparatus having a steam turbine, for liquefying thenatural gas from which carbon dioxide has been removed by the carbondioxide recovery apparatus,

(c) boiler equipment for supplying steam to the steam turbine of theliquefying apparatus, and

(d) a carbon dioxide recovery apparatus for combustion exhaust gasincluding an absorption tower for absorbing carbon dioxide fromcombustion exhaust gas exhausted from the boiler equipment by absorbingliquid, and a regeneration tower for separating and recovering carbondioxide from the absorbing liquid;

absorbing and removing carbon dioxide of natural gas by the absorbingliquid in the carbon dioxide recovery apparatus for natural gas;

liquefying the natural gas from which carbon dioxide has been removed bythe carbon dioxide recovery apparatus for natural gas;

absorbing and removing carbon dioxide of combustion gas exhausted fromthe boiler equipment by the absorbing liquid in the carbon dioxiderecovery apparatus for combustion exhaust gas; and

regenerating the absorbing liquid by separating and recovering carbondioxide from the absorbing liquid containing carbon dioxide in theregeneration tower of the carbon dioxide recovery apparatus forcombustion exhaust gas.

In the method for producing liquefied natural gas, it is preferable thatthe absorbing liquid containing carbon dioxide absorbed by the carbondioxide recovery apparatus for natural gas and the absorbing liquidcontaining carbon dioxide absorbed by the carbon dioxide recoveryapparatus for combustion exhaust gas are regenerated by the sameregeneration tower.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a schematic diagram showing an LNG production plant used in anembodiment of the present invention; and

FIG. 2 is a schematic diagram of a CO₂ recovery apparatus installed inthe LNG production plant shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Now, the LNG production plant according to the present invention will beexplained in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of LNG production plant used in anembodiment of the present invention, and FIG. 2 is a schematic diagramof a CO₂ recovery apparatus installed in the LNG production plant shownin FIG. 1.

The LNG production plant comprises a CO₂ recovery apparatus 10, anatural gas liquefying apparatus 40 having a steam turbine (not shown),a boiler 50 serving as a power source, and a compressor 62 driven by,for example, a steam turbine 61.

A natural gas passageway 701 is connected to the CO₂ recovery apparatus10, which is connected to the boiler 50 through a combustion exhaust gaspassageway 702. The CO₂ recovery apparatus 10 comprises a cooling tower11, a combustion exhaust gas absorption tower 12, a natural gasabsorption tower 13, and a regeneration tower 14, all being arrangedadjacent to each other.

The cooling tower 11 incorporates a gas-liquid contact member 15. Thecombustion exhaust gas absorption tower 12 incorporates upper and lowergas-liquid contact members 16 a and 16 b. An overflow portion 17 for aregenerated absorbing liquid is arranged between the gas-liquid contactmembers 16 a and 16 b. The natural gas absorption tower 13 incorporatesupper and lower gas-liquid contact members 18 a and 18 b. An overflowportion 19 for a regenerated absorbing liquid is arranged between thegas-liquid contact members 18 a and 18 b. The regeneration tower 14incorporates upper and lower gas-liquid contact members 20 a and 20 b.

The cooling tower 11 is connected to the boiler 50 through thecombustion exhaust gas passageway 70 ₂. Cooling water is sprayed to theupper portion of the cooling tower 11 through the circulating passageway70 ₃, so a combustion exhaust gas introduced through the passageway 70 ₂is cooled with the gas-liquid contact member 15. The top of the coolingtower 11 is connected to near the lower portion of the combustionexhaust gas absorption tower 12 through a passageway 70 ₄. A blower 21is inserted in the passageway 70 ₄.

The bottom of the combustion exhaust gas absorption tower 12 isconnected to a heat exchanger 22 through the passageway 70 ₅, which isequipped with a pump 23.

The natural gas passageway 70 ₁ is connected to the lower portion nearthe bottom of the natural gas absorption tower 13. The bottom of theabsorption tower 13 is connected to the heat exchanger 22 through thepassageways 70 ₆ and 70 ₅. The passageway 70 ₆ is equipped with a pump24.

The heat exchanger 22 is connected to the portion located between theupper and lower gas-liquid contact members 20 a and 20 b of theregeneration tower 14 by a passageway 70 ₇.

The bottom of the generation tower 14 is connected to the upper portion(that is, to the overflow portion 17) of the combustion exhaust gasabsorption tower 12 through a passageway 70 ₈ (which passes through theheat exchanger 22), and also connected to the upper portion (theoverflow portion 19) of the natural gas absorption tower 13 through apassageway 70 ₉, which is branched from the passageway 70 ₈. The pump 25is attached on the passageway 70 ₈ between the bottom of theregeneration tower 14 and the heat exchanger 22.

In the combustion exhaust gas absorption tower 12, one of the ends ofthe passageway 70 ₁₀ is connected to the overflow portion 17 and theother end is connected to the portion of the tower 12 right above thegas-liquid contact member 16 a via a pump 26. An exhaust passageway 70₁₁ is connected to the top of the absorption tower 12.

In the natural gas absorption tower 13, one of the ends of thepassageway 70 ₁₂ is connected to the overflow portion 19 and the otherend is connected to the portion of the tower 13 right above thegas-liquid contact member 18 a via a pump 27. The one of the ends of apassageway 70 ₁₃ is connected to the top of the absorption tower 13 andthe other end is connected to the natural gas liquefying apparatus 40.Note that a dewatering apparatus is attached to the passageway 70 ₁₃.

In the regeneration tower 14, one of the ends of a passageway 70 ₁₄ isconnected to the lower portion near the bottom of the regeneration tower14 and the other end is connected to the portion of the regenerationtower 14 right under the gas-liquid contact member 20 b. A heatexchanger (reboiler) 28 is attached to the passageway 70 ₁₄. Apassageway 70 ₁₅, which flows through low-pressure steam derived fromthe steam turbine 61 of the compressor 62 and the steam turbine (notshown) of the natural gas liquefying apparatus 40, crosses at thereboiler 28. The low pressure stream is heat-exchanged with theregenerated absorbing liquid which flows through the passageway 70 ₁₄ atthe reboiler 28 and condensed.

In the regeneration tower 14, one of the ends of a passageway 70 ₁₆ isconnected to the top of the regenerator 14 and the other end isconnected to the compressor 62 via a heat exchanger 29 for cooling. Apassageway 70 ₁₇ is branched off the passageway 70 ₁₆ downstream of theheat exchanger 29 and connected to the regeneration tower 14 at theportion right above the gas-liquid contact member 20 a.

The boiler 50 is connected to the steam turbine 61 for driving thecompressor 62 by the passageway 70 ₁₈ feeding a high-pressure steam. TheCO₂ recovery apparatus 10 is connected to the compressor 62 by the flowpassage 70 ₁₆. CO₂ gas is supplied to the compressor 62, compressed, andexhausted out of the system though a passageway 70 ₁₉.

The boiler 50 is connected to the steam turbine (not shown) of thenatural gas liquefying apparatus 40 through a passageway 70 ₂₀, whichflows through high-pressure steam, and drives the apparatus 40 by thesteam turbine.

The natural gas liquefying apparatus 40 liquefies natural gas(containing not more than 50 ppm CO₂) which is supplied from the naturalgas absorption tower 13. The liquefied natural gas (LNG) flows throughthe passageway 70 ₂₁ and stored in a predetermined tank.

One of the ends of a passageway 70 ₂₂ is connected the steam turbine 61and the other end is connected to the passageway 70 ₁₅, which flowsthrough low-pressure steam from the steam turbine (not shown) of thenatural gas liquefying apparatus 40. The passageway 70 ₁₅ is connectedto the reboiler 28 of the regeneration tower 14.

The passageways 7015 which flows through low-pressure steam derived fromthe steam turbine of the natural gas liquefying apparatus 40 and fromthe steam turbine 61 of the compressor 62, crosses at the reboiler 28.However, either one of the low-pressure streams may be introduced to thereboiler 28.

Now, a method for producing LNG will be explained with reference to theLNG production plant shown in FIGS. 1 and 2.

First, natural gas is supplied to the lower portion near the bottom ofthe natural gas absorption tower 13 of the CO₂ recovery apparatus 10(shown in FIG. 2) through the natural gas passageway 70 ₁. The naturalgas goes up through the lower gas-liquid contact member 18 b of thenatural gas absorption tower 13. During this process, the natural gascomes into contact with a regenerated absorbing liquid (e.g., aregenerated amine solution), which is supplied from the regenerationtower 14 to the overflow portion 19 through the passageway 70 ₈ and thepassageway 70 ₉ (branched off the passageway 70 ₈) via a heaterexchanger 22, thereby absorbing CO₂ contained the natural gas. Thenatural gas further goes up through the overflow portion and the uppergas-liquid contact member 18 a and comes into contact with theregenerated amine solution supplied to the upper portion near the top ofthe natural gas absorption tower 13 through the passageway 70 ₁₂ withthe help of the function of the pump 27. As a result, CO₂ of the naturalgas remaining unabsorbed is absorbed by the amine solution until theconcentration of CO₂ becomes 50 ppm or less. The amine solutioncontaining CO₂ is stored at the bottom of the absorption tower 13. Also,H₂S contained in natural gas is absorbed and removed during this CO₂absorption step.

The natural gas from which CO₂ has been removed is supplied to a naturalgas liquefying apparatus 40 through the passageway 70 ₁₃. When thenatural gas flows through the passageway 70 ₁₃, a moisture content isremoved by a dewatering apparatus (not shown) arranged thereto. Thenatural gas liquefying apparatus 40 is driven by supplying high-pressuresteam generated by the boiler 50 to the steam turbine (not shown) of theliquefying apparatus 40 through the passageway 70 ₂₀ and liquefies thenatural gas dewatered. LNG is fed out from the passageway 70 ₂₁ andstored in a predetermined tank. Since the CO₂ level of the natural gasto be liquefied is as low as 50 ppm or less, dry ice is not produced inthe natural gas liquefying process.

The high-pressure steam is generated in the boiler 50 and supplied tothe steam turbine 61 for driving the compressor 62 through thepassageway 70 ₁₈. In the boiler 50, high-pressure steam is generated byburning a fuel (e.g., natural gas). Therefore, a large amount ofcombustion exhaust gas containing CO₂ generates.

The combustion exhaust gas is supplied in its entirety to the coolingtower 11 of the CO₂ recovery apparatus 10 (shown in FIG. 2) through thecombustion exhaust gas passageway 70 ₂ and cooled by cooling watersupplied through the passageway 70 ₃ while passing through thegas-liquid contact member 15. The cooled combustion exhaust gas issupplied from the top of the cooling tower 11 to the lower portion nearthe bottom of the combustion exhaust gas absorption tower 12 through thepassageway 70 ₄ with the help of the blower 21. The combustion exhaustgas goes up through the lower gas-liquid contact member 16 b in theabsorption tower 12 and comes into contact with a regenerated aminesolution, which is supplied from the regeneration tower 14 to theoverflow portion 17 through the passageway 70 ₈ via the heat exchanger22, thereby absorbing CO₂ contained in the combustion exhaust gas by theamine solution. The combustion exhaust gas further passes through theoverflow portion 17 and the upper gas-liquid contact member 16 a. Duringthis process, the combustion exhaust gas comes into contact with theregenerated amine solution, which is supplied to the portion near thetop of the absorption tower 12 through the passageway 70 ₁₀ with thehelp of the function of the pump 26. As a result, CO₂ of the natural gasremaining unabsorbed is absorbed. The amine solution containing CO₂ isstored at the bottom of the absorption tower 12. On the other hand, thecombustion exhaust gas from which CO₂ has been removed is exhausted outof the system through the exhaust passageway 70 ₁₁.

The amine solution containing the absorbed CO₂ and stored at the bottomof the combustion exhaust gas absorption tower 12 is supplied to theheat exchanger 22 through the passageway 70 ₅ with the help of thefunction of the pump 23. Similarly, the amine solution containing theabsorbed CO₂ and stored at the bottom of the natural gas absorptiontower 13 is supplied to the heat exchanger 22 through the passageway 70₆ (which is merged into the passageway 70 ₅) with the help of the pump24. When the amine solution containing the absorbed CO₂ passes throughthe heat exchanger 22, it is heat-exchanged with a regenerated aminesolution having a relatively high temperature and supplied through thepassageway 70 ₈ connected to the bottom of the regeneration tower 14. Asa result, the amine solution containing the absorbed CO₂ is heated,whereas the regenerated amine solution is cooled.

The amine solution containing CO₂ heated by the heat exchanger 22 issupplied to the portion located between the gas-liquid supply members 20a and 20 b of the regeneration tower 14 through the passageway 70 ₇ andgoes up through the lower gas-liquid contact member 20 b. During thisprocess, the amine solution containing CO₂ is separated into CO₂ and aregenerated amine solution. The regenerated amine solution is stored atthe bottom of the regeneration tower 14, circulated through thepassageway 70 ₁₄ and heat-exchanged at the reboiler 28, at which thepassageway 70 ₁₄ crosses the passageway 70 ₁₅, which flows through thelow-pressured steam fed from the natural gas liquefying apparatus 40 andthe steam turbine 61. Since the regenerated amine solution is heated asdescribed, the temperature of the regeneration tower 14 itself increasesand used as a heat source for separating the regenerated amine solutioninto CO₂ and regenerated amine solution.

The regenerated amine solution is stored at the bottom of theregeneration tower 14 and fed back to the combustion exhaust gasabsorption tower 12 through the passageway 70 ₈ and to the natural gasabsorption tower 13 through the passageways 70 ₈ and 70 ₉ (branched from70 ₈), respectively, with the function of the pump 25.

The CO₂ exhaust separated by the regeneration tower 14 goes up throughthe upper gas-liquid contact member 20 a and exhausted from the topthrough the passageway 70 ₁₆. When the CO₂ exhaust flows through thepassageway 70 ₁₆, it is cooled by the heat exchanger 29 to condenseamine vapor contained in the CO₂ exhaust into amine solution, which isfed back to the regeneration tower 14 by way of the branched passageway70 ₁₇.

After CO₂ contained in natural gas and combustion exhaust gas is removedby the CO₂ recovery apparatus 10, CO₂ is supplied to the compressor 62through the passageway 70 ₁₆. At this time, high-pressure steam issupplied from the boiler 50 to the turbine 61 through the passageway 70₁₈ to drive the turbine 61. When the compressor 62 is driven by theturbine 61, CO₂ supplied to the compressor is compressed and exhaustedout of the system, for example, by supplying it to a urea plant,methanol plant, dimethyl ether plant, lamp oil/light oil synthesizing(GTL) plant, or the ground, through the passageway 70 ₁₉. Note that whenthe compressed CO₂ is used as a raw material for a urea plant, methanolplant, dimethyl ether plant, or lamp oil/light oil synthesizing (GTL)plant, H₂S contained in the compressed CO₂ is removed.

The low-pressure steam fed from the steam turbine 61 passes through thepassageway 70 ₂₂, merges into low-pressure steam supplied from the steamturbine of the natural gas liquefying apparatus 40 and flowing throughthe passageway 70 ₁₅, and enters the CO₂ recovery apparatus 10. In theCO₂ recovery apparatus 10, more specifically, at the reboiler 28, thelow-pressure steam is exchanged with the regenerated amine solutioncirculated through the passageway 70 ₁₄. As a result, the regeneratedamine solution is heated and conversely the low-pressure steam is cooledto condense into water. The condensed water is fed back to the boiler 50(as a boiler water) through the passageway 70 ₁₅.

According to embodiments of the present invention, when liquefiednatural gas (LNG) is produced from natural gas by the natural gasliquefying apparatus 40, CO₂ is recovered from the natural gas and thecombustion exhaust gas generated in the boiler 50 by the CO₂ recoveryapparatus 10, and the recovered CO₂ is supplied to the compressor 62driven by the steam turbine 61, which is driven by supplyinghigh-pressure steam from the boiler 50, compressed and discharged out ofthe system. In this way, no CO₂ or less amount of CO₂ is exhausted fromthe boiler 50. Since the amount of CO₂ is reduced, CO₂ emission tax isreduced. It is favorable in view of economy and preventing globalwarming.

Furthermore, CO₂ can be efficiently used by supplying compressed CO₂from which H₂S has been removed, to a urea plant, methanol plant,dimethyl ether plant, or lamp oil/light oil synthesizing (GTL) plant.However, when the aforementioned plants are not arranged adjacent to theLNG production plant, the compressed CO₂ is supplied into the groundsuch as an oil well or gas well for producing natural gas to fix it.

Furthermore, in the CO₂ recovery apparatus 10 for recovering CO₂ fromnatural gas or combustion exhaust gas, which is generated by the boiler50 serving as a power source, the combustion exhaust gas absorptiontower 12 and the natural gas absorption tower 13 share the regenerationtower 14. By virtue of this structure, the CO₂ recovery apparatus 10 canbe reduced in size and, by extension, the entire LNF production plantcan be miniaturized.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A plant for producing liquefied natural gascomprising: a carbon dioxide recovery apparatus for natural gasabsorbing and removing carbon dioxide from natural gas; a liquefyingapparatus having a steam turbine, for liquefying the natural gas fromwhich carbon dioxide has been removed by the carbon dioxide recoveryapparatus; a boiler equipment for supplying steam to the steam turbineof the liquefying apparatus; and a carbon dioxide recovery apparatus forcombustion exhaust gas including an absorption tower for absorbingcarbon dioxide from combustion exhaust gas exhausted from the boilerequipment by absorbing liquid, and a regeneration tower for separatingand recovering carbon dioxide from the absorbing liquid.
 2. The plantfor producing liquefied natural gas according to claim 1, wherein thecarbon dioxide recovery apparatus for natural gas has an absorptiontower for absorbing and removing carbon dioxide from natural gas by anabsorbing liquid, and an regeneration tower for separating andrecovering carbon dioxide from the absorbing liquid, the regenerationtower also serving as the regeneration tower of the carbon dioxiderecovery apparatus for combustion exhaust gas.
 3. The plant forproducing liquefied natural gas according to claim 2, further comprisesa compressor equipped with a steam turbine for compressing carbondioxide separated and recovered from the absorbing liquid.
 4. The plantfor producing liquefied natural gas according to claim 3, wherein thesteam turbines installed in the compressor and the liquefying apparatusare driven by steam generated by the boiler equipment.
 5. The plant forproducing liquefied natural gas according to claim 3, wherein theregeneration tower of the carbon dioxide recovery apparatus furthercomprises a reboiler using low-pressure steam supplied from at least oneof the steam turbines as a heat source.
 6. A method for producingliquefied natural gas comprising the steps of: providing a plant forproducing liquefied natural gas comprising: (a) a carbon dioxiderecovery apparatus for natural gas absorbing and removing carbon dioxidefrom natural gas, (b) a liquefying apparatus having a steam turbine, forliquefying the natural gas from which carbon dioxide has been removed bythe carbon dioxide recovery apparatus, (c) boiler equipment forsupplying steam to the steam turbine of the liquefying apparatus, and(d) a carbon dioxide recovery apparatus for combustion exhaust gasincluding an absorption tower for absorbing carbon dioxide fromcombustion exhaust gas exhausted from the boiler equipment by absorbingliquid, and a regeneration tower for separating and recovering carbondioxide from the absorbing liquid; absorbing and removing carbon dioxideof natural gas by the absorbing liquid in the carbon dioxide recoveryapparatus for natural gas; liquefying the natural gas from which carbondioxide has been removed by the carbon dioxide recovery apparatus fornatural gas; absorbing and removing carbon dioxide of combustion gasexhausted from the boiler equipment by the absorbing liquid in thecarbon dioxide recovery apparatus for combustion exhaust gas; andregenerating the absorbing liquid by separating and recovering carbondioxide from the absorbing liquid containing carbon dioxide in theregeneration tower of the carbon dioxide recovery apparatus forcombustion exhaust gas.
 7. The method for producing liquefied naturalgas according to claim 6, wherein the absorbing liquid containing carbondioxide absorbed by the carbon dioxide recovery apparatus for naturalgas and the absorbing liquid containing carbon dioxide absorbed by thecarbon dioxide recovery apparatus for combustion exhaust gas areregenerated by the same regeneration tower.
 8. The method for producingliquefied natural gas according to claim 7, wherein the carbon dioxideseparated and recovered from the absorbing liquid in the regenerationtower is compressed by a compressor having a steam turbine andthereafter exhausted out of the system.
 9. The method for producingliquefied natural gas according to claim 8, wherein the steam producedby the boiler equipment is supplied to each of the steam turbines of thecompressor and the liquefying apparatus.
 10. The method for producingliquefied natural gas according to claim 8, wherein the regenerationtower of the carbon dioxide recovery apparatus further has a reboilerand low pressure steam supplied from at least one of the steam turbinesof the compressor and the liquefying apparatus is used as a heat sourceof the reboiler.